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Discussion Starter #1
is this true?
they said at the exhaust shop that its not mandatory(sp?) to run an o2 sensor for just around town but on long trips you need one.
that doesnt sound right?
can someone please clear this up for me?

thanks
jamie...
 

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Discussion Starter #3
sorry buddy
i dont know all that much about engines, so could you please explain to me what the purpose of an o2 sensor is?
im guessing its something to do with the air/fuel ratio's right?
 

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feeding your habit
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the 02 sensor provides feedback to the ECU and lets the ECU know how to modify the pulse (width) it sends to the injectors.

On cold start the engine runs off a map, also at idle. Once you go past these points, the engine runs in closed loop control, meaning the ECU reads the O2 sensor output and modifies injector signal accordingly.

-M
 

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maybe he was referring to the post-cat sensors which only detect if the cats are working or not. if i am not mistaken, people who run a catless downpipe delete the secondary 02 sensors, at least that is how it is with my truck.
 

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well thats how that o2 sensor works also. the ecu reads what one sensor says then it reads what the o2 sensor behind the cat says and makes adjustments. that will also tell you if you have a bad cat but i don't think its there to just tell you if you cat is bad or not.
 
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Bank 1 (front O2 sensors) are mandatory smog equipment in OBD I and OBD II cars. Bank 2 (rear, after cat sensors) are mandatory in OBD II cars.

Removing them is a smog equipment violation.

Removing the fronts will mess up your fuel trims, both Strim and Ltrim (short and long) and will throw codes. Your car will run rich or lean, and response may be off. The more you drive it like this, the worse it should get. Do not under any circumstances operate a fuel injected vehicle with the front O2 sensors removed unless you know what you are doing and are experienced (tuning, etc.).

Removing the rear will also throw a light on the dash and a code. It will only tell you either the O2 sensor is not working, or the Cat has lost all efficiency (like you run leaded gas or something). Lead + cat convertors = dead. You can remove the rears and watch the dash light tell you to check codes and nothing will ever happen.
 

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98mkiv said:

On cold start the engine runs off a map, also at idle. Once you go past these points, the engine runs in closed loop control, meaning the ECU reads the O2 sensor output and modifies injector signal accordingly.

-M
Also... the car will go into open loop at around 75 percent throttle, whiche means it runs off maps, and ignores the oxygen sensor
 

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I'm not sure that removing the o2 sensors will run foul of the law, we don't have the same smog rules here in Australia.

Jamie, like said here and on the other forum, you wsant the o2 sensors, besides the ecu having a hissy fit, the o2 sensor keeps your air:fuel ratios in check when you're cruising in closed loop mode.
 

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im about to fit my single and when done will need to get the car to an exhaust shop to get the downpipe made. is it possible to drive my car there without the o2 sensor? its about 5 miles
 
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If you have an obd1 and have a downpipe and removed the CAT, what will the second o2 sensor be doing? mine is not throwing any codes and remains connected.

thanks
 
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The JDM TT does have the main O2 sensor, but no the 2nd (post-cat) sensor.

The car runs pig-rich if you remove/unplug the O2 sensor.
 
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